CHEMISTRY LAB

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Transcript of CHEMISTRY LAB

Test for Reducing Property of SugarsOther Test:

Iodine TestHydrolysis of SucroseExperiment No. 17:Carbohydrates ChemistryCarbohydrates are polyhydroxy carbonyl compounds or those substances that produce them upon complete hydrolysisColor Reactions And TestsOsazone TestMolisch TestSeliwanoff's TestMucic Acid TestCompostion of ReagentPhenylhydrazine HCL + Sodium AcetatePROCEDUREOsazone Testa.k.a Phenylhydrazine TestThis test is used to identify sugars whose stereochem differed by one chiral carbon and for monosaccharides.ResultCompostion of Reagenta-naphtol + ethanolMolisch TestGeneral test for Carbohydratea sensitive chemical test for the presence ofPROCEDUREresultpurple ring @ junctionSchiff's TestFuchsin + Sodium Bisulfite + HClcomposition of reagentSchiff's TestIt is a qualitative test performed in order to detect the possible presence of aldehydesprocedureresultcomposition of reagentconc. resorcinol + HClSeliwanoff's Testa chemical test which distinguishes between aldose and ketose sugarsprocedureresultreddish brownmagentacomposition of reactionH2O + HNO3procedureMucic Acid Testa test for identification of galactose which is a component of antigensresultpresence of crystalsFehling's Testcomposition of reagentFehling's A: CuSO4 + NaOHFehling's B: Na-K tatrateFehling's TestIt is a test to distinguish between reducing sugars and non-reducing sugarsprocedureresultBenedict's Testcomposition of reactionCuSO4 + Na2CO3 Benedict's TestIt is a test for the presence of reducing sugarsprocedureTollen's Testcomposition of reagentAgNO3 + NaOH resultbrick red- positivelight blue- negativeTollen's TestIt is a test to distinguish aldehyde and ketoneprocedureresultpale yellow-negativesilver mirror-positivePicric Testcomposition of reagentphenol + HNO3 Picric Acid TestIt is a test used to determine the presence and the levels of reducing sigarsprocedureyellowsucroseBarfoed's Testcomposition of reagent Copper Tartrate + Acetic acidBarfoed's TestA test used for detecting the presence of monosaccharideprocedureresultcomposition of reagentI2 + KI + H20Iodine TestIt is a test for detection of polysaccharide to differentiate bet. starch, dextrin, and glycogenprocedureresultHydrolysis of starch

Carbohydates and 1-2 diols gives a positive result to this test.monosaccharides, isaccharides, and polysaccharides should give a positive reaction which is a purple ring at junction of two liquids. Nucleic acids and glycoproteins also give a positve reactionThis test gives a positve result to carbohydrates with an aldehyde functinal group. Dark pink - purple color indicates a positive result The test reagent dehydrates ketohexoses to form 5-hydroxymethylfurfural which further rects with resorcinol present in the test reagent to produce a red to reddish brown product within two minutes or less. Aldohexoses form the same product, but do so very very slowly.This test is used for reducing sugars which have free aldehyde or ketone group. Cupric ion complex with tarttrate ion is reduced to cuprous oxide. a positive result is indicated by the formation of brick red precipitateBenedict's reagent is used as a test for the presence of reducing sugars. This includes all monosaccharides and the disaccharides , lactose and maltose. Thus, although the ketose fructose is not strictly a reducing sugar, it is an alpha- hydroxy - ketone , and gives a positive test because it is converted to the aldoses glucose and mannose by the base in the reagent. Carbohydrates which react with Benedict's reagent to reduce the blue copper (II) ion to form a brick red precipitateFormation of a silver mirror is an indication of a positive resultThe test is similar to the Fehling's reaction with aldehydes. It is based on the reduction of copper acetate to copper oxide which forms a brick red precipitatecolorlessAmylose in starch is responsible for the formation of a deep blue color in the presence of iodine. The iodine molecule slips inside of the amylose coil.A blue-black color results if starch is present. Thus, this test will give a negative result to glucose and sucrose.yellow osazone crystalprocedureIodine Test ResultReaction of Hydrolyzed StarchStarch is a non reducing polysaccharide therefore it does not give positive result with Benedict’s, Fehling’s. Tollen's and Barfoed’s reagents, nor does it form any Osazone.However after hydrolysis into monosaccharide by the actions of strong acid , its components (glucose molecules) giveall the test positive.The body uses the monosaccharide glucose as its source of energy. In order for energy to be obtained from sucrose, starches and other saccharides, the organism must first break them down into glucose. This reaction entails the hydrolysis of the glycosidic linkages catalyzed by a collection of enzymes. However, in this experiment, we used HCl as a catalyst.PROCEDUREWhat is the importance of HCl in hydrolysis of starch? Starch is made up of a long chain of glucose molecules held together by glycosidic bonds. One carbon in the ring is bound to an oxygen which is bound to the carbon of another ring: this is the glycosidic bond. This C-O-C bond, an ether linkage, can be broken through hydrolysis to release the constituent glucoses.

Hydrochloric acid puts H+ in your solution. The lone pairs of the oxygen in the C-O-C bond will attack this H+. Now oxygen is bound to three things; it is unstable. Because acid allows this destabilization to occur, it lets hydrolysis of the bond occur.chemistry laboratoryHydrolyzed starch with Fehlingsprocedureresult